The present invention relates to a road surface roughness measuring apparatus for measuring the roughness of a road surface at the same position, wherein a rotary type unit for measuring the coefficient of dynamic friction measures the coefficient of dynamic friction of the road surface.
There are many conventional technologies for measuring the coefficient of dynamic friction of the road surface. According to such conventional technologies, a measuring unit is pulled by a tractor and separately measures the roughness and the coefficient of dynamic friction of the road surface. However, in general, the measurement values of the coefficient of dynamic friction tend to produce errors depending upon the measuring units. In order to correct such errors in the measurement values of the coefficient of dynamic friction, usually, the relationship between the coefficient of dynamic friction and the roughness of the road surface is determined; and then, an international friction index (IFI) value is determined based on such relationship.
In order to determine the IFI value, it is necessary to measure the roughness and the coefficient of dynamic friction at the same position of the road surface. However, it was considerably difficult to measure the two values (the roughness and the coefficient of dynamic friction) at the same position of the road surface.
As to the measurement of the coefficient of dynamic friction, the applicant discloses technical contents relating to a rotation type device for measuring the coefficient of dynamic friction in Japanese Patent Application Publication No. 3-10062. However, such technical contents (disclosed in Japanese Patent Application Publication No. 3-10062) are used for measuring the coefficient of dynamic friction of the road surface in the shape of a circle. In other words, such technical contents are not used for measuring the roughness of the road surface. Accordingly, in order to determine the IFI value, another apparatus for measuring the roughness at the same position is necessary. Therefore, there has been desired an apparatus which is able to measure the road surface roughness and the coefficient of dynamic friction in detail at a plurality of sections on the same measuring path as the measuring circle of the rotation type device.
The present invention has been provided to solve the above-mentioned problem. The object of the present invention is to provide a road surface roughness measuring apparatus for measuring the coefficient of dynamic friction and the roughness of the road surface in each direction at a same section where the coefficient of dynamic friction is measured. The apparatus divides the measuring circle on the road surface into a plurality of sections, on which measuring circle the rotary type unit for measuring the coefficient of dynamic friction measures the coefficient of dynamic friction.
The present invention is a road surface roughness measuring apparatus being combined with a rotary type unit for measuring the coefficient of dynamic friction, which apparatus comprises: a frame having a plurality of legs provided for placing the apparatus on a road surface; a rotary shaft mounted on such the frame and extending in vertical direction; a rotary encoder mounted on the top end of such the rotary shaft; a rotation plate mounted on the bottom end of such the rotary shaft; a motor being combined with a speed reducing means and driving the rotary shaft via gears; and a laser displacement gauge mounted on the above-mentioned rotation plate.
The laser displacement gauge is disposed so as to measure by the rotation of the above-mentioned rotation plate along a measuring circle, on which circle the rotary type unit for measuring the coefficient of dynamic friction measures the coefficient of dynamic friction.
The apparatus has a function for dividing the measuring circle into a plurality of sections and a function for calculating the road surface roughness for each section based on the signals of the laser displacement gauge and the rotary encoder.
According to the road surface roughness measuring apparatus of the present invention, the apparatus is placed at the same position on the road surface, where the rotary type unit for measuring the coefficient of dynamic friction measures the coefficient of dynamic friction, is rotated along the same path on which path the rotary type unit for measuring the coefficient of dynamic friction measures the coefficient of dynamic friction, and measures the road surface roughness. The measurement of the road surface roughness is carried out by measuring the distance from the measuring circle to the laser displacement gauge, which is mounted on the rotation plate being rotated by the motor combined with the speed reducing means. The measurement of road surface roughness is carried out according to the sampling signal of the rotary encoder and calculating the roughness. Then, the measuring circle is divided into the plurality of sections and the road surface roughness is outputted as a mean profile depth (hereinafter referred to as a MPD) value, for example, for each divided section.
Therefore, it is possible to measure the roughness in the plural directions and the coefficient of dynamic friction at the same position; and thus, it is possible to carry out a more analytical research by the use of this more detailed road surface data.
In this connection, when carrying out the present invention, if the coefficient of dynamic friction is measured first, rubber and the like or water is attached to the road surface. Therefore, it is preferable that the roughness is measured first.
When carrying out the present invention, it is possible to measure the road surface roughness in the entire area within the measuring circle.